1. Field of the Invention
The present invention relates to a cantilever allowing observation of physical properties of samples, and to a method of manufacturing the cantilever.
2. Description of the Related Art
A cantilever for an ordinary scanning probe microscope (SPM) is mounted through semiconductor crystal etching or the like. The maximum value of a distal end diameter of a probe of a cantilever is usually specified in specifications, whereas the minimum value thereof is not particularly specified, that is, it is not a known value. This is because there is a demand for a probe as thin as possible. Thus, with the current state of the art, when the probe is brought into contact with the sample, it is rather difficult to keep the contact area therebetween at a known value.
When measuring physical properties of a surface of a sample, for example, viscoelasticity or the like of the sample surface, by using a cantilever, in order to perform accurate measurement, it is desirable that a contact area between the sample and the probe be a known value and that the measurement be conducted under a fixed pressure while controlling the pushing force. That is, the deformation amount of the sample is a value proportional to the pressure, so, if the measurement is conducted with solely the force set, it is rather difficult to meet the above-mentioned requirement with a cantilever with an ordinary probe as described above.
In this connection, a cantilever is known which adopts a spherical configuration of a specified diameter (see, for example, JP 2002-62253 A and JP 10-170530 A). Generally speaking, in manufacturing a cantilever of this type, there is adopted a method in which a spherical body is fixed to a distal end of a conventional probe by adhesive or the like or a method in which a spherical body is fixed to a distal end of a flat lever portion by adhesive or the like and is used as a probe.
In the cantilever, which has a spherical probe of a predetermined diameter, it is possible for the contact area between the probe and the sample to be a know value. Thus, it is possible to accurately measure physical property, such as viscoelasticity.
However, in manufacturing the conventional cantilever described above, the following problems are still involved.
That is, when bonding the spherical body to the distal end of a pointed probe or to the distal end of a flat lever portion, an operator usually conducts a bonding operation by using a manipulator while checking parts to be bonded. Thus, the operation is rather difficult to perform and requires experience, which means it is not to be easily performed just by anybody; the operation can only be performed by a skilled operator.
In particular, when bonding the spherical body, setting of a position of the spherical body is difficult to perform. Further, it is necessary to apply a predetermined amount of adhesive solely to a predetermined position, such as the distal end of a probe or the distal end of a lever portion, so the operation is difficult to perform even for a skilled operator.
Further, the above-mentioned method only allows handling of a spherical body of a size allowing observation with an optical microscope, so a further reduction in the contact area between the probe and the sample is impossible. Further, the fact that the spherical body has to be manipulated by a manipulator also makes it necessary for the spherical body to be of a size not smaller than a fixed level so that it can be handled properly, which means handling of a minute spherical body is impossible.
Further, after application of adhesive, the operator must quickly mount the spherical body before the adhesive is cured. That is, the operator is compelled to quickly perform a delicate and precise mounting operation. This restriction in terms of time also makes the mounting operation difficult to perform.
Further, even when the mounting operation is conducted by a skilled operator, it can happen that the adhesive is applied in excess, resulting in a surface of the spherical body being excessively covered with a part of the adhesive. Thus, there is a fear of a change in the contact area between the probe and the sample, that is, a fear of a deterioration in product quality.
Further, in some cases, when using a cantilever, the spherical body is previously modified with some substance according to the use. In the conventional method, which requires a number of steps for the mounting operation, if the modification is effected on the spherical body-prior to the adhesion, the modified portion will be damaged or affected by the adhesive. In view of this, instead of performing the modification on the spherical body beforehand, there is nothing for it but to modify the spherical body together with the cantilever after it has been mounted to the cantilever. However, when the modification is performed on the spherical body together with the cantilever, there is a fear of the cantilever being adversely affected; thus, there are limitations in terms, for example, of the kind of substance to be used for modification, thus making the handling of the spherical body and the cantilever rather difficult. Further, this also leads to a deterioration in terms of a degree of freedom in design.